1. Field of the Disclosure
The present disclosure relates to reducing memory and power usage in digital radio broadcast receivers.
2. Background Information
Digital radio broadcasting technology delivers digital audio and data services to mobile, portable, and fixed receivers. One type of digital radio broadcasting, referred to as in-band on-channel (IBOC) digital audio broadcasting (DAB), uses terrestrial transmitters in the existing Medium Frequency (MF) and Very High Frequency (VHF) radio bands. HD Radio™ Technology, developed by iBiquity Digital Corporation, is one example of an IBOC implementation for digital radio broadcasting and reception.
IBOC digital radio broadcasting signals can be transmitted in a hybrid format including an analog modulated carrier in combination with a plurality of digitally modulated carriers or in an all-digital format wherein the analog modulated carrier is not used. Using the hybrid mode, broadcasters may continue to transmit analog AM and FM simultaneously with higher-quality and more robust digital signals, allowing themselves and their listeners to convert from analog-to-digital radio while maintaining their current frequency allocations.
One feature of digital transmission systems is the inherent ability to simultaneously transmit both digitized audio and data. Thus the technology also allows for wireless data services from AM and FM radio stations. The broadcast signals can include metadata, such as the artist, song title, or station call letters. Special messages about events, traffic, and weather can also be included. For example, traffic information, weather forecasts, news, and sports scores can all be scrolled across a radio receiver's display while the user listens to a radio station.
IBOC digital radio broadcasting technology can provide digital quality audio, superior to existing analog broadcasting formats. Because each IBOC digital radio broadcasting signal is transmitted within the spectral mask of an existing AM or FM channel allocation, it requires no new spectral allocations. IBOC digital radio broadcasting promotes economy of spectrum while enabling broadcasters to supply digital quality audio to the present base of listeners.
Multicasting, the ability to deliver several audio programs or services over one channel in the AM or FM spectrum, enables stations to broadcast multiple services and supplemental programs on any of the sub-channels of the main frequency. For example, multiple data services can include alternative music formats, local traffic, weather, news, and sports. The supplemental services and programs can be accessed in the same manner as the traditional station frequency using tuning or seeking functions. For example, if the analog modulated signal is centered at 94.1 MHz, the same broadcast in IBOC can include supplemental services 94.1-2, and 94.1-3. Highly specialized supplemental programming can be delivered to tightly targeted audiences, creating more opportunities for advertisers to integrate their brand with program content. As used herein, multicasting includes the transmission of one or more programs in a single digital radio broadcasting channel or on a single digital radio broadcasting signal. Multicast content can include a main program service (MPS), supplemental program services (SPS), program service data (PSD), and/or other broadcast data.
The National Radio Systems Committee, a standard-setting organization sponsored by the National Association of Broadcasters and the Consumer Electronics Association, adopted an IBOC standard, designated NRSC-5, in September 2005. NRSC-5 and its updates, the disclosure of which are incorporated herein by reference, set forth the requirements for broadcasting digital audio and ancillary data over AM and FM broadcast channels. The standard and its reference documents contain detailed explanations of the RF/transmission subsystem and the transport and service multiplex subsystems. Copies of the standard can be obtained from the NRSC website at nrscstandards.org. iBiquity's HD Radio technology is an implementation of the NRSC-5 IBOC standard. Further information regarding HD Radio technology can be found at iBiquity's websites at hdradio.com and ibiquity.com.
Other types of digital radio broadcasting systems include satellite systems such as Satellite Digital Audio Radio Service (SDARS, e.g., XM Radio, Sirius), Digital Audio Radio Service (DARS, e.g., WorldSpace), and terrestrial systems such as Digital Radio Mondiale (DRM), Eureka 147 (branded as DAB Digital Audio Broadcasting), DAB Version 2, and FMeXtra. As used herein, the phrase “digital radio broadcasting” encompasses digital audio broadcasting including in-band on-channel broadcasting, as well as other digital terrestrial broadcasting and satellite broadcasting.
Typical digital radio broadcast receiver implementations at the highest level of functionality require dynamic memory allocations in amounts that may be too large for cost and size optimization. Reducing the amount of required memory may typically be done, to a degree, without affecting functionality. However, such reduction may eventually lead to reduced performance, which may be reflected in slower receiver response and limited instantaneous information regarding services that are available but are not selected for current use. Further memory reduction may result in reduced receiver functionality, and may not be acceptable in some cases.
One particular operation that involves large amounts of receiver memory is deinterleaving. Block-based techniques of deinterleaving in digital radio receivers are processor intensive and typically require two full tables of addresses in memory. Thus, reducing the memory requirements for deinterleaving could result in significant memory and power reduction at the digital radio broadcast receiver.
In addition, typical receiver implementations employ complete processing of the physical layer (Layer 1), which is in excess of the actual content and bit rate of the data being rendered by the receiver. In the case of audio, the presence of more than one audio service can lead to deinterleaving and decoding audio services that a user does not hear, therefore wasting receiver processing resources and memory. In the case of data, data services may be delivered within any logical channel, each of which may contain several sub-channels. Therefore, when a receiver becomes aware of a data service, it may have to process numerous logical channels and sub-channels to render only one service of interest. Again, this additional processing is wasteful of receiver processing and memory resources.
The present inventor has found that digital radio broadcast receivers can be implemented with reduced memory and power requirements by improving the deinterleaving memory and operation's efficiency and/or minimizing other unnecessary operations.